Heterojunction structure with a charge compensation layer formed between two group III-V semiconductor layers

Abstract

A thin film crystal wafer with pn-junction comprising a first layer of a first conductivity type which is a 3-5 group compound semiconductor represented by a general formula: InxGayAlzP (0<=x<=1, 0<=y<=1, 0<=z<=, x+y+z=1), and the second layer of a first conductivity type which is a 3-5 group compound semiconductor represented by a general formula: InxGayAlZ,As (0<=x<=1, 0<=y<=1, 0<=z<=1, x+y+z=1), said second layer being made above said first layer, and at a heterojunction interface formed between said first layer and said second layer, further comprising a charge compensation layer of a first conductivity type with an impurity concentration higher than that of said first and second layers.

What is claimed is:  
     
       1. A thin film crystal wafer with pn-junction comprising a first layer of a first conductivity type which is a 3-5 group compound semiconductor represented by a general formula: In x Ga y Al z P (0≦x≦1, 0≦y≦1, 0≦z≦, x+y+z=1), and the second layer of the first conductivity type which is a 3-5 group compound semiconductor represented by a general formula: In x Ga y Al Z As (0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1), said second layer being made above said first layer, and at a heterojunction interface formed between said first layer and said second layer, further comprising a charge compensation layer of a first conductivity type with an impurity concentration higher than that of said first and second layers, and the thickness of said charge compensation layer is not less than 1 nm and not more than 15 nm; 
       wherein a carrier concentration and thickness of said charge compensation layer are controlled depending on a bandgap energy of said first layer.  
     
     
       2. A thin film crystal wafer with pn-junction according to  claim 1 , further comprising a collector layer and a base layer, wherein said first layer is a semiconductor layer which serves as an emitter layer with a band gap larger than said base layer. 
     
     
       3. A thin film crystal wafer with pn-junction according to  claim 1  or  2 , wherein said first layer is an n-type InGaP layer and said second layer is an n-type Al x Ga y As layer (0≦x≦1, 0≦y≦1, x+y=1). 
     
     
       4. A thin film crystal wafer with pn-junction according to claims  1  or  2 , wherein said first conductivity type is an n-type and an n-type impurity is Si. 
     
     
       5. A thin film crystal wafer with pn-junction according to claims  1  or  2 , wherein the impurity concentration of said charge compensation layer is greater than 1×10 18  cm −3 . 
     
     
       6. A thin film crystal wafer with pn-junction according to claims  1  or  2 , wherein said first layer has a thickness of not more than 60 nm. 
     
     
       7. A thin film crystal wafer with pn-junction according to claims  1  or  2 , wherein sheet doping amount Ns (cm −2 ) that is a product of carrier concentration and thickness of said charge compensation layer satisfies: 
       
         
           (180 ×ΔEg +3.0)×1 E 11 ×C 1 >Ns >(160 ×ΔEg− 4.6)×1 E 11 ×C 2  
         
       
       wherein 
       ΔEg=(1.92−(Eg+ 1×Δy)),    
       C1=((dInGaP/30){circumflex over ( )}(−1.0))×(−2.1E−17×Ndemitter+26.8)/16.2×(1.2×dn+GaAs+9.8)/15.7  
       C2=((dInGaP/30){circumflex over ( )}(−1.59))×(−1.7E−18×Ndemitter+14.9)/6.5×(0.61×dn+GaAs+3.5)/6.6×(−7.5E−18×NdGaAs+10.4)/6.6  
       wherein 
       Eg is a bandgap energy of the first layer at room temperature (eV),  
       Δy is obtained by subtracting a value of In composition of the first layer when the first layer coincides with the second layer in lattice constants from a value of the In composition of said first layer,  
       dInGaP is a thickness of the first layer (nm),  
       Ndemitter is a carrier concentration of the first layer (cm −3 ),  
       dn+GaAs is a thickness of a charge compensation layer (nm), and  
       NdGaAs is a carrier concentration of the second layer (cm −3 ).  
     
     
       8. A thin film crystal wafer with pn-junction according to claims  1  or  2 , wherein epitaxial growth of each of said layers is performed in organometal vapor-phase growth method.